Accelerometer



Nov. II, 1941. P. KOLLSMAN 2,262,007

ACCELEROMETER Filed March 30, 1939 s Sheets-Sheet 1 INVENTOR Pa u] Ko/Zsman (-44 ATTORNEY P., KOLLSMAN ACCELEROMETER Nov. 11, 1941.

Filed March 30 1939 5 Sheets-Sheet 2 INVENTOR Paul Kaila/nan BY 9 a i I kw ATTORNEY No 11, 1941. P. KO LSMAN 2,262,007 v ACCELEROMETER Filed March 30, 1939 5 Sheets-Sheet 5 a mm m N /.5 N. W 0 m WK NOV. 11, 1941. p, KOLLSMAN 2,262,007

AGCELEROMETER Filed March.30, 1939 5 Sheets-Sheet 4 ATTORNEY Nov. 11, 1941. P. KOLLSMAN ACCELEROMETER 5 Sheets-Sheet 5 Filed March 30, 1939 INVENTOR Paul l1ollsm'an M W ATTORNEY Patented Nov. 11, 1941' UNITED STATES PATENT OFFICE ACCEIEROMETER Paul Kollsman, New York, -N. 1., assignor, by mesne assignments, to Square D Company, Detroit, Mich.I a corporation of Michigan Application March 30, 1939, Serial No. amaze 3 Claims.

This invention relates in general to instruments for measuring the rate of change of velocity of moving bodies and more particularly to nism to indices whereby the acceleration or deceleration may be readily observed in desirable measuring units.

More specifically, a pair of cooperating levers,

- each weighted at one end and fixed at the opposite end to a pivotally mounted arbor, are arranged to swing about their respective axes in overlapping relation when the instrument is moved at an accelerating or decelerating speed. The arrangement of the levers is such that the extent of rotation of the weights about their axes is a function of the magnitude of acceleration or deceleration. Furthermore, the lever systems are so arranged as to permit a long range of movement of the weighted masses whereby to minimize errors due to vibration or other forces not wanted in an acceleration measurement.

Suitable gearing is provided to transmit the rotative movement of the weighted levers to a rotatable shaft carrying a momentary reading or continuously indicating pointer. This main pointer shaft is provided with a 'disc having means to actuate a second shaft mounted concentric with the main pointer shaft. This second shaft carries a maximum reading pointer. The mechanismtransmitting the movementof the main pointer shaft to the other pointer shaft is such that the pointer of the second shaft will indicate the maximum acceleration for any given movement of the instrument.

Each weighted lever system is provided with I with novel means for protecting the delicate parts from breakage or damage when the instrument is subjected to unusual forces or excessive acceleration.

The operating mechanism may be compact and mounted in a casing having the advantages of occupying but small space.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Some features of this invention having general application toindicating instruments are further described and claimed in my co-pending application Serial No. 361,574, filed October 17,

Further aims, objects and advantages of this invention will appear from a consideration of the description and the accompanying drawings showing for purely illustrative purposes embodiments of this invention. It is to be understood,

however, that the description is not to be taken in a limiting sense, the scope of this invention being defined in the appended claims.

Fig. 1 is a side elevation with the casing shown insection; I

Fig; 2 is a plan view of the face of the instrument after it has made a recording;

Fig. 3 is a plan section on line 33 of Fig. 1

Fig. 4 is a fragmentary plan section on line 4-4 of Fig. 1;

Fig. 5 is a section on line 5'-5 of Fi 1 looking toward the face of the instrument;

Fig. 6 is an enlarged fragmentary section on line 6-6 of Fig. 2;

of a hair spring about one of the pointer shafts when the instrument is in normal or zero position corresponding to Fig. 8;

Fig. 9 is a diagrammatic view showing the pointers or hands at the instant of maximum normal reading of the instrument when both hands have moved around to the maximum range of the instrument in normal use;

Fig. 10 is a diagrammatic view showingthe instrument brought to rest after an accelerated movement leaving the maximum reading pointer inposition;

Fig. 11 is a diagrammatic view showing the pointers in the position they assume under abnormal shock conditions;

Fig. is a fragmentary view of the hair 1 an adjustably secured spring holder 43.

spring shown in Fig. 8a but corresponding to the position of the pointers shown in Fig. 11;

Fig. 12 is a diagrammatic view showing the momentary reading pointer returned to zero position leaving the maximum reading pointer in the position shown in Fig. 11; and

Fig. 13 is a digrammatic view for further facilitating description.

In the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

In the drawings accompanying and forming part of this specification, a practical commercial embodiment of the invention is shown, but as such illustration is primarily for purposes of disclosure, it will 'be understood that the structure may be modified in various respects without departing from the spirit and scope of the invention as hereinafter defined and claimed.

Referring now to the drawings, in which like reference characters denote like parts in the sevof illustration, comprises a housing ID in which is mounted a frame ll affording support for the operating parts.

The frame, which may be of cast metal, comprises a face wall l2, a pair of standards l3 and I4 and a rear wall l which may be in the shape of an open ring. Extending from the rear wall are a plurality of lugs l6, l1, and Ill. The housing or casing ID of generally cup shape form,

-eral figures, the instrument, shown for purposes which may be of metal, a phenol condensation product, or other suitable material, comprises a cylindrical sidewall portion I9, a rear wall and an open end which may be'enclosed with a transparent disc 2| may be of glass or other desirable transparent material. The glass disc 2| may abut a ring 22 and be removably held in place by a split clamping ring 23. Shoulders 21 extending from the housing provide means for conveniently securing the instrument to the mov- I Mounted in the frame II are a pair of substantially symmetrical lever systems. A weighted lever comprising a weight and an arm 3| is fixedly mounted at its opposite end 32 to an arbor 33. Arbor 33 may be pivotally mounted and, as shown, journals 34 and 35 at the opposite ends of the arbor may be J'ournaled in suitable bearings 35 and 31 mounted in the face and rear walls respectively of the frame I l. A set screw 28 may be provided for adjustment of the bearing 31.

Fixedly mounted on the arbor 33 is an outwardly extending arm 38 adapted to provide a pivot connection with a spring holder 39. The arm 38 in adapted to fit in the bifurcated end 40 of the spring holder and a pivot pin 41 extends through openings in the bifurcated end 40 and the arm 38 to provide the pivot connection just mentioned. g

A helical retention spring 42 is. fixed at one end to the spring holder 39 and at the other to The spring'holder 43 may be provided with a threaded portion 44 extending into a female threaded opening 45 in the frame ll. pull or restraining force of the spring 42 may be varied and adjusted. A set screw 46 may be provided for maintaining the spring holder 43 in adjusted position.

Also fixedly mounted to arbor 33 is a gear segment 41 secured at its axis 48 to the arbor 33. This gear segment intermeshes with a corresponding gear segment fixed to the other lever system.

The other lever system likewise comprises a weighted lever having a weight 50 and an arm 5|. It is fixed at its opposite end 52 to an arbor 53. Arbor 53 may be mounted in similar fashion as arbor 33. As shown, journals 54 and 55 at its opposite ends may be journaled in bearings 56 and 51 mounted in the face wall l2 and rear wall l5 respectively of the frame II. A set screw 29 may be provided for adjustment of the hearing 51. V Fixedly mounted on the arbor 53 in an outwardly extending arm 58 corresponding to the arm 38 of the opposite lever system. It is pivotally connected by a pivot pin- 6| to a spring holder 53 having a bifurcated end 60.

A helical retention spring 62 corresponding to helical spring 42 is secured at one end to the spring holder 53 and at its opposite end to an adjustably secured spring holder 63. This spring holder 63, corresponding to spring holder 43 may be provided with a threaded portion 64 extending 'into a female threaded opening 65 in the frame H. Thus, the restraining force of spring 62 may be varied and adjusted. A set screw 66 may be provided for maintaining the spring holder 43 and consequently the spring 62 in predetermined adjustment in the same fashion as the spring 42.

Secured to arbor 53 is a segment gear 61 secured at its axis 58 to arbor 53. This gear segment 5! meshes with gear segment 41.

It will now be apparent that there'are two lever systems provided which are operatively interconnected, each having its own adjustable yieldable restraining means. The arbors 33 and 53 provide rocker shafts and any swingable movement of one of the weighted levers within the range of their movement is correspondingly transmitted to the opposite lever system operating in the opposite direction through the intermeshing gear segments 41 and 51. The levers will swing in overlapping relationship between a the axes of arbors 33 and 53 within the housplane and the lever arms varies; This variation might be compensated for by a corresponding ing III.

Moreover, the weighted masses 30 and 50 may travel in an arcuate path in a relatively long arc and have freedom to move approximately equal amounts on either side of a plane through the axes of'the arbors 33 and 53 which arbors form the pivots about which the lever arms 3| to acceleration being measured exerts the greatest moment about the pivots of the arborsv 33 and 53 (see Fig. 3).

It will be noted that the moment tending to swing the levers on their respective axes will vary when the angle between the above-mentioned calibration of the scale on the dial of the instrument. However, in accordance with the inven- Consequently, the

tion, this variation may be compensated for in the following manner.

The arms 38 and 58 extend substantially radially from the axes of their respective arbors 33 and 53 and at substantially right angles to the respective lever arms 3I and 5|. The springs 42 and 82 are pivoted to the arms 38 and 58 respectively and are anchored at their respective opposite ends to spring holders 43 and 83.

It will be observed that, as the weighted levers swing about their axes in response to an accelerated movement of the device in the direction acceleration is being measured, the efiective length of each of these lever arms 3I and 5| varies as the angle varies between each of these lever arms and a plane through the axes of arbors 33 and 53. Thus, the moment tending to swing each weighted lever about its axis will vary as. the angle varies. Simultaneously, the resisting force of the restraining springs 42 and 82. is also varied in the same proportion, since the effective length of each of the lever arms 38 and 58 varies corresponding to the variation of the efiective lengths of lever arms 3| and 5I. Thus, ascale of uniform graduations may be used to measure acceleration accurately since the variation of the eifective lengths of the weighted lever arms has been, so to speak, subjected to mechanical compensation.

Secured to the arbor 33 is a segment gear,89 which meshes with a pinion I8 carried by atransmission mechanism, described more in detail hereinafter. v

Pinion I8 is secured to an enlarged portion II of a rotatable shaft I2, the outer end of which is provided with a pointer I3 adapted upon rotation of the shaft to traverse the scale 28 of the dial 25 (see Fig. 7). The innerend of the shaft I2 provides a journal II which may be provided with a slotted bushing or ring I5 preventing axial thrust between shaft II and a member 88 later to be described. A cross member I8 secured by screws I'I toilugs I8 extending inwardly from face-wall I2 of the frame II,provi'des a rigid spaced relation support for the journal I4 and the slotted ring I5.

A hub 19 is secured to the enlarged portion II of the shaft I2. It may have secured thereto a hair spring 88. The inner end of this hair spring may be secured to the hub 19 and the outer end may be secured to a stake 8| secured to the cross member I8. Thus, undesirable play or back lash Also secured to the sleeve 85 is a disc 9| provided with ratchet teeth 92 at its periphery. A

click member or pawl 93 (seeFig. 5) which may be a leaf spring is secured at one end to a bracket 98 on the inner surface of the face wall I2 of the frame II. The opposite end 95 of this leaf spring or pawl is bent substantially at right angles to the main portion thereof and is adapted to frictionally engage the ratchet teeth 92 of the disc 9| to hold same in any position to which it has been moved by the normal operation of the instrument. The end 95 functions asa resilient member acting in a plane substantially at a right angle to the plane of the main portion of the spring pawl 93 and is adapted to eliminate any inching or stepping of the toothed wheel 9I which might be induced by vibration or shock of the instrument as distinct from normal movement thereof. The resilient spring pawl 93 is mounted so that normally the end 95 is urged against the ratchet teeth 92. However, a lever 98 pivotally secured as by a screw 9! to the frame II is adapted to engage the spring 93 and disengage the end 95 from the ratchet teeth 92. A second spring 98 fixed at one end to bracket 94 and engag ng the lever through. a notch 99 normally urges the lever 98 away from the spring 93.

- This notch is struck out from a protruding shoulder I88 on the lever 98. The opposite end of this lever is also provided with a shoulder I8I extending outwardly therefrom. It is adapted to be engaged by a pin I82 extending from a shaft I83 journaled in the walls of a protruding portion I84 (see Fig. 6) of the housing or casing I8.

Shaft I83 is provided with a knurled hand knob I85 accessible at the outside of the housing. A spiralspring I88 normally urges the pin I82 away from the shoulder I8I of the lever 98. Upon rotation of the knob I85 to rotate the pin I82 in the direction of the shoulder I8 I, the lever, upon engagement of the pin I82 and shoulder I8I, will cause the opposite shoulder I88 of the lever to engage the spring 93 and release the end 95 from the ratchet teeth. Upon release of the of the shaft I2 and pointer I3 may be eliminated when these parts are actuated.

There is also secured to the enlarged portion II 'of the shaft 12, a disc 82 carrying near its periphery a pin 83, the purpose of which is pointed out hereinafter.

Journaled in bearing 84 in the face wall I2 of the frame II is a sleeve 85 concentric with shaft I2 and mounted to rotate about said shaft. The enlarged portions 88 and 81 of the shaft I2 provide bearing surfaces for the inner surface of the sleeve 85. The outer end of this sleeve may be provided with a pointer 98 adapted, upon rotation of the sleeve, to traverse thescale 28 of the dial 25. This pointer 98, as is pointed out in further detail hereinafter, provides a maximum reading pointer or hand, while the pointer I3 provides a momentary reading pointer or hand.

Rotatably mounted on a hub 88 secured to or knurled knob I the 'pin I82 is disengaged from the shoulder I8I and the lever returned to normal position allowing the spring 93 again to engage the ratchet disc 9I. Hence, the end ofspring 93 normally is in frictional engagement with the ratchet teeth 92.

Disc 9I is also provided with a pin I88 near its periphery which is adapted to be engaged by the floating arm 89 for a purpose described hereinafter.

Means providing a snubbing action for the sleeve 85 and maximum reading pointer 98 may comprise a'hub II8 (see Fig. 7) of relatively large diameter which may be secured to or formed integral with a disc III which may have a smaller hub II2 whereby it may be securely fixed to the sleeve 85; A hair spring II3 having its tecting walls to prevent snarling of the hair.

spring H3. The hair spring in addition to its arrangement for snubbing action also tends to 'prevent play and back-lash of the sleeve and pointer 98 when they are actuated.

The frame II is also provided with a plurality of'leaf springs, I28, I2I, I22 and I23. One endin oppoiste directions.

of each may be secured to the frame as by screws 124. The opposite ends of these springs may uring the acceleration of a moving body is as follows: It may be assumed that the instrument is given a movement in the direction of which acceleration is to be measured. The centers of gravity of the weighted levers 3| and 5| are away from their axes of rotation. By reason of the inertia of the masses, the'levers are caused to swing in overlapping relation about their axes of rotation. This causes a rotation in opposite directions of the arbors 33 and 53. The rotation is transmitted in balanced relation through the intermeshing gear segments 41 and 61. By providing two corresponding lever systems, in accordance with the invention, forces in directions along axes other than that in which acceleration is to be measured are balanced out. If the instrument is tilted from a horizontal plane, the action of gravity upon the weighted levers will be counteracted since the action is transmitted from one lever system to the other Furthermore, by providing each lever systemwith its own adjustable resilient restraining springs 42 and 62, driving'friction between gear segments 41 and 81 is minimized or substantially eliminated and, as pointed out, they compensate for the arcuate movement of the weighted masses 38 and 58, all of which tends to greater accuracy of the instrument.

The extent of rotation or swinging of the weights 30 and 58 about their axes is a function of the magnitude of rate of change of velocity in a given movement of the instrument. Accordingly, this rotation is transmitted by the arbor or rocker shaft 33 through the driving gear seg ment 88 to cause a corresponding rotation of the pinion III.

The pinion Ill being secured to the main shaft 12 will cause a corresponding rotation of the pointer I3. Since the lever systems, gear segment 69, pinion I0 and shaft 12 are in constant operatively connected engagement, the pointer 13 will constantly indicate momentary changes of acceleration or deceleration in the direction of which rate of change of velocity is being measured. The quantitive measurement may be indicated on the uniformly graduated scale of the dial which is traversed by the pointer. In the instrument shown, the reading may be in 9 units. It will be observed that in the particular graduation of the scale of the instrument shown, one revolution of the pointer 13 indicates nine gs. Itwill be apparent that other graduations may be used and the instrument may be correspondingly calibrated prior to use.

Hence, it will be seen that in a given movement of the instrument, rate of change of velocity may be read at any instant by observing the pointer 13. Since rate of change of velocity will effect a corresponding movement of the weights 30 and 50, there will be a corresponding relative movement of the pointer 13 over the scale 26.

Should it be desired to measure the maximum i acceleration for any given movement of the in:

strument this may be accomplished with facility. When the instrument is normally at rest, the pointers l3 and 80, the disc 82, the ratchet disc 8|, the floating arm 89 and the hair spring 3 will be in the positions shown diagrammatically in Figs. 8 and 8a. If the instrument is given an accelerated movement the maximum of which is to be measured, the weighted levers are caused to swing as described in the foregoing. This will cause arbor 33 to rock the segment 68 to rotate the pinion 10 which in turn causes a corresponding rotation of the shaft 12 and the driving disc 82 in a clockwise direction. Pin 83 on disc 82 will engage the floating arm 88 causing it to rotate or swing about its axis of rotation. The floating arm in turn will engage pin 188 of the ratchet disc SI and cause this disc to be rotated in the same direction. Since the disc 3| is secured to the sleeve 85, it will cause the pointer 90 to be rotated in the same direction.

Referring now more specifically to Fig. 9, showing diagrammatically that the instrument has been given an acceleration of ten as. '(One revolution of the pointer 13 indicates nine gs on this particular scale.) The momentary reading pointer 13 will have made a rotation as indicatedby the arrow line a and the maximum reading pointer will have been given a corresponding rotation indicated by the arrow line b.

If the instrument is then brought to constant velocity the momentary reading pointer 13 will return to zero on the scale 28 as indicated by arrow line 0 (Fig. 10) because this pointer, as pointed out hereinbefore, is in constant operative connection with the lever systems. The lever systems will be returned to normal zero position when the instrument comes to constant velocity or to rest by reason of the action of the two retention springs 42 and 82.

It will be observed that the pointer 13 and the discs 82 returning to zero position as indicated in Fig. 10 will not operate disc 9| since the floating arm is not engaged by pin 83 until disc 82 has travelled almost a complete revolution in a counter clockwise direction. In the meantime, pin I08 has not been moved although pin 83 has engaged arm 89 on the opposite side. Hence, pointer 90 is retained at its position of maximum acceleration and will remain there. This has been brought about by reason of the hair spring 3 and the frictional engagement of the spring pawl 93 which temporarily holds the disc 9| from further rotation in either direction.

To reset the maximum reading pointer to zero; for example, when another maximum reading for a given movement of the instrument is to be made, the knurled knob I05 may be rotated to actuate lever 88 in turn to disengage the pawl 93 from the ratchet disc 8|. Thereupon the hair spring H3 which has in the meantime been at least partially wound up on the hub I M will cause the disc 9| to rotate and return it to normal zero position. The instrument and its parts will then again be in the position shown diagrammatically in Fig. 8.

Inusing and shipping instruments of the character comprehended by the invention, it often happens that they are subjected to abnormal forces or shocks and to accelerations far exceeding the calibrated range of the instrument. It has sometimes been the practice to provide locking devices for the moving parts to protect the instrument when being shipped or when not in use. In accordance with the present invention, a

snubbing arrangement is provided whereby an independent, locking device is not necessary. Furthermore, this arrangement protects the delicate parts from damage, injury or breakage even though the instrument is given abnormal shocks and excessive acceleration either when being shipped or handled or when in use.

To illustrate this feature of the invention, it may be assumed that the instrument is subjected to an abnormal force such as being dropped. Such a fall may impart an abnormal acceleration tending to rotate both the momentary reading indicator l3 and the maximum reading indicator 90 beyond the normal workable range of the instrument. According to the invention, however, when such acceleration is imparted to the' instrument, the hair spring H3 will wind itself upon the hub I I0. The hub I I is so proportioned that a relatively big wind-up" of the spring results from a relatively small rotation of the hub. It is so adjusted that the action of the maximum reading pointer will be gently but effectively snubbed, on say, one and one-half revolution of the maximum reading pointer. Hence, the momentum of the rotating pointer will not carry the delicate parts beyond a predetermined limit and no shocks will be imparted to them to damage or break them as otherwise would be the result of subjecting the instrument to such abnormal forces.

Fig. 11 and Fig. 11a show diagrammatically the hair spring windup and snubbing effect when the instrument is subjected to an abnormally great acceleration. It will be observed that momentary reading pointer 13 has reached its range of movement and will be restrained by the relatively strong retention springs 42 and 62 since the lever systems are in constant operatively connected engagement with the shaft 12 (see Fig. 1). On the other hand, pointer 90 and the hollow shaft 85 to which it is' secured will tend to rotate further dueto the momentum imparted to it by the shock of the excessive acceleration. The hair spring H3 and the ratchet.

disc 9| and pawl 93 provides some restraining force but not suflicient to prevent a tendency to spin the pointer 90. However, by reason of the maximum windup of the hair spring 3 on the hub N0 the rotation of pointer 90 is efiectively snubbed at a predetermined point as indicated in Figs. 11 and 11a. Thus, if the instrument is given an abnormally great acceleration, the delicate parts of the instruments will be protected from damage and breakage.

Referring now to Fig. 12 there is shown diagrammatically the position of the floating arm 89 with the instrument brought to constant speed or to rest and the momentary pointer returned to zero. The maximum reading pointer 90 remains at maximum acceleration indication until the instrument is reset as described hereinbefore. A simple turn of the knob I will cause the spring H3 to unwind and return the pointer 90 to zero position.

Referring now to Fig. 13 there is shown diagrammatically what might be expected to happen but for the snubbing action of the hair spring of disc 82 with a butting action. This undesirto the delicate parts of the instrument. In accordance with the invention, however, this undesirable result is eliminated.

Furthermore, the soft stops provided by the leaf springs I20, l2l, I22 and I23, prevent the weights and 50 of the lever systems from striking the casing wall IS with abrupt shock ment inoperative for protection to the operative parts in shipping and handling.

Obviously, the present invention is not restricted to the particular embodiments herein shown and described, but may be modified without departing from the'spirit of the present invention.

What is claimed is:

l. A device for measuring accelerations in the direction of a predetermined axis of response, comprising, in combination, a support; a first --and a second lever pivotally mounted on said support; a mass carried'by each of said levers, the levers being so disposed that accelerations in the direction of the said axis of response cause pivotal movement of one lever inclockwise and of the other lever in counter-clockwise direction, during which movement said masses move along arcsabout the pivotal axes of the levers thereby changing the length of their eifective lever arms with respect to the acceleration forces in the direction of said axis of response; a restraining helical spring for each of said levers connected between the respective lever and the support for expansion and contraction in the direction'of the spring axis, the points of application of thespring at the lever and at the sup port being so selected that the effective lever arm on which the spring acts on the lever changes in its length corresponding to the change in length of the efiective lever arm of the mass on said combination, a support; a first and a second bellcrank lever pivotally mounted on said support for movement in overlapping relationship; a mass carried by one arm of each of said bell-crank levers thereby moving on an are about the pivotal axes at a lever arm of varying efiective length with respect to acceleration forces acting along said predetermined axis; a pair of intermeshing gears connected to said first and second bell-crank lever,- respectively; a restraining spring for each of said bell-crank levers connected between. said support and said other arm able action would result in breakage of or damage of said bell-crank lever, said other arm being so disposed as to change its effective length of lever arm on which the spring acts corresponding to the change in efiective length of said one arm carrying said mass; and indicatingmeans connected. to one of said bell-crank levers to show the movement of said lever about said pivotal axis.

3. A devicefor measuring accelerations in the in combination, a support; a first and a second bell-crank lever pivotally mounted on said support for movement in overlapping relationship; a mass carried by one arm of each 01 said bellcrank levers, thereby moving on an are about the pivotal axes at a lever arm of varying effective length with respect to acceleration forces acting along said predetermined axis; a pair of direction of a predetermined axis comprising.-

ing helical spring for each of said bell-crank levers connected between said support and said other arm of said bell-crank lever to be distorted for elongation, said other arm being so disposed as to change its effective length of lever arm on. which the spring acts corresponding to the change in effective length of said one arm carrying said mass; and indicating means connected-to one of said bell-crank levers to show the moveintermeshing gears connected to said first and i0 ment of said lever about said pivotal axis.

second bell-crank lever, respectively; a restrain- PAUL KOLLSMAN. 

